One of the most pressing problems in cancer research is that little is known concerning the reasons why tumor cells invade adjacent tissues and produce secondary tumors in distant parts of their host. Recent experimental evidence suggests that the invasiveness of metastatic potential of tumor cells is determined by their cell surface properties. In a murine model system utilizing various variant B16 melanoma cell lines, it was demonstrated that cell lines with higher metastatic potentials (defined by the formation of more metastases) could be derived by a regimen of passing tumors from secondary sites into tissue culture, then reimplanting intravenously, and repeating the process several times. Using this procedure, cell lines have been derived by Dr. I.J. Fidler which are highly metastatic and produce significantly more secondary tumors than the parent line. We propose to use these cell lines grown in vivo as ascites tumors or in vitro in tissue culture to determine if cell surface properties are responsible for the metastatic properties of tumor cells, and to characterize the cell surfaces of metastatic, highly metastatic and non-metastatic tumors. Chemical, enzymatic and ultrastructural techniques will be utilized to study cells grown in vitro and in animals. Surface enzymatic activities (proteases such as fibrinolytic enzymes and glycosidases such as hyaluronidase, sialidase, etc.) will be investigated with radioisotope assays. Cell adhesive characteristics will be examined by quantitative cell aggregation using a particle counting assay and monolayer attachment assay. Cell surface antigens will be identified using cytotoxic and quantitative absorption assays, and surface saccharides will be identified by plant lectin agglutination and quantitative labeling. Ultrastructural localization of specific antigens and saccharides will be determined using ferritin-conjugated antibodies and lectins, and certain cell surface constituents such as sialic acid will be assayed by chemical procedures. The information gathered will be utilized to modify experimental metastasis with the goal of reducing secondary tumor formation. BIBLIOGRAPHIC REFERENCES: Nicolson, G.L. and Winkelhake, J.L: Organ specificity of blood-borne tumour metastasis determined by cell adhesion? Nature 255: 230-232 (1975).